While there's been Anti-Americanism in Europe ever since the bloody colonials broke with Mother England, it took quite a few years for it to develop within.
Fred Siegel has a rather nice read here in Commentary Magazine on exactly this topic.
Read the whole thing, of course, but here is the final paragraph:
The rhetorical tropes fashioned in the 1920s, and restated repeatedly over the decades since, were reflections, DeVoto made clear, not so much of America as of a funhouse-mirror version of it, a distorted refraction based on aesthetic conceits and social pretensions. DeVoto died in 1955, so he never saw his fears realized by the rebirth of the anti-American intellectual in the 1960s. Today that spirit can be found in precincts both high and low—from the hallways of academe to late-night infotainment comics such as Jon Stewart and Stephen Colbert, who traffic in a knowing snarkiness that confers an unearned sense of superiority on their viewers. Now, as then, angered by the impertinence of the masses in their increasing rejection of the hope and change promised them in 2008, liberals, as in the title of a recent article in the online magazine Slate, raise themselves up by shouting, "Down with the People!"
While clearly not quote of the same caliber as the romantic-inspired Anti-Americanism of the Europeans, there remains a common thread, one that continues to cripple meaningful thought on the Left (such that the Left remains capable of such though): that of elitism, that the common man is to be despised and looked down upon.
As if the Left knew anything of the common man: their knowledge here is distorted at best. Superiority unearned leads to a sense of entitlement, combined with a fundamental knowledge that it is unearned and that they are hence actually unworthy: this contradiction gnaws at the conscience. But since you can create quit a career by riding this wave, most suppress this guilt and are happy to live with their consciences.
You can be an American and be quite Anti-American at the same time. The Democratic Party is living proof of this.